Thermodynamically controlled chemical regeneration of spent battery cathodes using recyclable electron donors under ambient conditions

Devising an energy-efficient, profitable, and safe technology to recycle lithium-ion batteries (LIBs) is crucial for their continuous adoption in electric vehicles and grid energy storage. Herein, using recyclable electron donors (REDs) for which the redox potentials range between cathode operation and over-lithiation potentials, we establish thermodynamically controlled Li-coupled electron transfer from REDs to cathodes as a viable route for directly regenerating spent cathodes in dry air at room temperature. Simple soaking of the spent cathode in a regeneration solution enables the complete recovery of the original chemical composition and capacity of the Li-deficient cathode through electron and Li-ion transfer from RED molecules and Li salts, respectively. The RED-based lithiation universally applies to cathode materials with heterogeneous Li loss, allowing the Li quantification and cathode separation processes to be bypassed for recycling. We further demonstrate the practical feasibility of this approach by regenerating spent cathodes from commercial 1-A h pouch cells. In addition, we show that the used regeneration solution can be refreshed by simply mixing with reductants for reuse in lithiation, thereby promising minimal cost and chemical waste for battery recycling. The proposed cathode regeneration method under ambient temperature and pressure will propel the development of facile and scalable LIB recycling technologies.